Means and method for stacking thin sheets

ABSTRACT

The present invention is for a method of stacking of thin sheets and a device for stacking of thin sheets according to the method. The sheets can be made from paper, plastic film or the like. The invention is primarily intended to be used in connection with print outs in computer centers delivering a continuous, rapid and lengthy flow of paper sheets. The paper is brought into the stacker on a conveyer (4) comprising a number of parallel bands arranged side by side, which are controlled by pulley wheels and supporting wheels (5, 6, 7, 8). The papers are delivered from the conveyer (4) in the slit between the paper stack (16) and a second conveyer (9) which also comprises a number of parallel bands arranged sidewise passing over pulley wheels (10 and 24). The paper stack is supported by several supports (14) each having a resilient supporting edge (17) towards the paper stack. The stacker can be turned and tilted around an axis (25) at right angle to the plane of the FIGURE.

The present invention concerns a method for stacking of thin sheets anda device for stacking of thin sheets according to the method. The sheetscan be made from paper, plastic film or the like. The invention isprimarily intended to be used in connection with print-outs in computercentres delivering a continuous, rapid and lengthy flow of paper sheets.

At larger computer centres there is often an almost continuousproduction of print-outs. The printers used for this purpose have agreat capacity and the speed of the paper can be up to 1 meter persecond, corresponding to 4-6 sheets per second.

The printed papers are collected in stacks for further handling. Asuitable height of a stack is up to 200 mm, which means that each suchstack contains more or less numerous sets of print-outs for differentadressees. In order to facilitate the further handling those parts ofthe stack which are intended for a certain adressee should be displacedrelative to the adjacent parts of the stack. Separating stacks byaddressee is particularly important with the use of certain high speedprinting devices that produce a high speed continuous printed sheetoutput which is subsequently split up into separate sheets, possiblyintended for different addressees. In order to facilitate this handling,the print-outs often have a bar code, either on each separate sheet oron the first and possibly the last paper for an addressee, whereupon thecontinuous paper sheets can be controlled by impulses which are receiveddirectly from the printer or by optical reading of the bar codes. It isthen important that there is no further displacement of the paper inrelation to other papers.

The invention will below be described more in detail with reference tothe embodiment shown in the accompanying FIGURE.

The device shown in the FIGURE has two stackers 2, 20 for collecting ofseparate sheets to stacks of suitable size. The papers arrive to thedevice on a conveyer 1 and are received in a paper switch 25 where thepaper is directed using air. The paper directed upwards is carried on tothe upper stacker 2 and papers directed downwards are brought to thelower stacker 20 by the conveyer 3. The two stackers are of identicaldesign and function. The paper is brought into the stack on a conveyer 4comprising a number of parallel bands arranged side by side, which arecontrolled by pulley wheels and supporting wheels 5, 6, 7, 8. The papersare delivered from the conveyer 4 in the slit between the paper stack 16and a second conveyer 9 which also comprises a number of parallel bandsarranged sidewise passing over pulley wheels 10 and 24. The paper stackis supported by several supports 14 each having a resilient support edge17 towards the paper stack. The stacker can be turned and tilted aroundan axis 26 at right angle to the plane of the FIGURE.

A paper incoming to the stacker from the conveyer 1 passes the paperswitch 25 and it directs the paper towards the upper stacker 2. Thepaper is caught onto the conveyer bands 4 and leave these after passingunder the pulley wheels 7. The paper is then directed at an angleinwards towards the paper stack 16 and is brought up so that it passesin between the stack and the conveyer bands 9. These bands passover-upper pulley wheels 11 and lower pulley wheels 24. The lower pulleywheels 24 are mounted onto a shaft which is mounted onto arms extendingup to the shaft 10 through the centre of the upper pulley wheels 11. Thelower pulley wheels 24 can swing freely in this suspension device and ifthe rear supports 14 are in a certain position the pulley wheels 24 movegradually when further paper is delivered to the stack. In connectionwith this movement a position switch 15 is affected by the pivotingarrangement of the pulley wheels 24. The supports 14 are arranged sothat they can be displaced in a direction towards or away from theconveyer bands 9. This displacement arrangement is effected by theposition switch 15 and as the paper stack increases the supports 14 aremoved away from the driving arrangement in small steps of 1-2 mm. Thepapers brought into the apparatus on the conveyer 1 are to have the texton the upper side. In this way the papers in the stack will be placed inorder with the first paper on top and the last paper on the bottom.

The maximum size of the stack is decided by the maximum allowed distancebetween the conveyer bands 9 and the supports 14. The desired size of acompleted stack can, however, be controlled by different criteria, e.g.by means of a counting device determining the number of sheets or bymeasuring the thickness or weight of the stack. The above mentioned barcodes can be used to control the stacking so that papers which belongtogether are not put into different stacks, but one stack is completedwith the last paper for a certain addressee.

When the last paper of a stack is directed to the correct stacker, thepaper switch 25 is shifted, which in this case means that the papers aredirected to the conveyer 3 and conveyed to the lower stacker 20 wherethe papers are collected as described for the upper stacker. When thelast paper has been put into position in the stacker 2, this is turnedaround the shaft 26 into a position which in the FIGURE is marked by apart of a stacker 20A. The forkshaped stopper 13, against which incomingpapers knock, is pivotally suspended from a shaft 12 and drops down to aposition under the upper part of the conveyer 9, so that the papers areno longer prevented from moving in a direction to the left in theFIGURE. In connection with the tilting of the stacker its driving motor18 is disconnected and the conveyer bands 9 are connected to the drivingconveyer 22. The stack is then brought out until it is on the conveyer22 in the position as shown in the FIGURE. The stacker has then beenemptied and is tilted back into its starting position, whereby also thesupports 14 are brought back to a position adjacent to the conveyerbands 9 and the stacker is then ready to receive new papers.

When the lower stacker 20 contains a completed stack this is deliveredin the same way as described above to a conveyer 21. This conveyer ismovable in a vertical direction and can be raised up to the positionmarked 21A and is then a part of a continuous conveyer comprising afirst conveyer band 22, the movable conveyer 21 and a final deliveryconveyer band 23. The transport of the stack sis controlled in such away that the upper paper of one stack on the conveyer 23 is the paperfollowing directly after the bottom paper in the preceding stack.

I claim:
 1. An apparatus for high speed continual stacking of aplurality of sheets connected to an initial sheet delivery conveyor fordelivering sheets to be stacked to the apparatus and to a final stackdelivery conveyor for removing stacked sheets from the apparatus, saidapparatus comprising:a plurality of sheet stacking devices of apredetermined capacity, each said stacking device comprising receivingmeans for receiving at least a portion of said plurality of sheets fromthe initial sheet delivery conveyor, stacking means connected to saidreceiving means for forming a stack of sheets from said at least aportion of said plurality of sheets, detection means for determiningwhen said stack has reached the predetermined capacity, and firstcontrol means for:(1) setting said stacking device to a stackingposition if the predetermined capacity is not reached, wherein saidstacking means is active and said stacking device is positioned andconfigured to receive at least a portion of said plurality of sheetsfrom the initial sheet delivery conveyor, and (2) setting said stackingdevice to an unloading position when said predetermined capacity isreached, wherein said stacking means is inactive and said stackingdevice is positioned and configured to deliver said stack to the finalstack delivery conveyor; and second control means, connected to saidfirst control means of each of said plurality of stacking devices and tothe initial sheet delivery conveyor, for directing a flow of saidplurality of sheets from the initial delivery conveyor away from a firststacking device of said plurality of stacking devices and toward asecond stacking device of said plurality of stacking devices when saidfirst stacking device is in said unloading position, and for causingsaid first control means of said second stacking device to set saidsecond stacking device into said stacking position when said pluralityof sheets is directed to said second stacking device; said secondcontrol means being further configured for directing said plurality ofsheets away from said second stacking device to said first stackingdevice when said second stacking device is in said unloading position,and for causing the first control means of said first stacking device toset said first stacking device into said stacking position to receivesaid plurality of sheets, so that said first and said second stackingdevices alternate in forming stacks from said plurality of sheetsreceived from the initial sheet delivery conveyor and in unloadingformed stacks to the final stack delivery conveyor, thereby continuallyproducing stacks of sheets.
 2. The apparatus of claim 1, furthercomprising means for selecting the predetermined capacity of at leastone stacking device of said plurality of stacking devices.
 3. Theapparatus of claim 1, wherein said detection means comprises at leastone of a counting means for counting a number of sheets in said stack,means for measuring a height of said stack, and means for measuring aweight of said stack.
 4. The apparatus of claim 1, wherein said stackingmeans comprises an adjustable stacking area, and wherein said receivingmeans comprises at least one conveyor for transferring each sheet ofsaid at least a portion of said plurality of sheets to said stackingarea.
 5. The apparatus of claim 1, further comprising a stack receivingmeans positioned between said plurality of stacking devices and thefinal delivery conveyor for transferring at least one stack from saidplurality of stacking devices to the final delivery conveyor, said stackreceiving means comprising:a vertically movable first conveyor having afirst end and a second end; a second conveyor having a proximal endaligned with said first stacking device when said first stacking deviceis in said unloading position, and a distal end; and third control meansfor activating said first conveyor and for raising said first conveyorinto an upper position, wherein said first end of said first conveyor ishorizontally aligned with the final stack delivery conveyor, when saidfirst stacking device is in said unloading position such that a stackdelivered from said first stacking device travels along said second andsaid first conveyors to the final stack delivery conveyor, and fordeactivating and lowering said first conveyor to a lower positionwherein said second end of said first conveyor is aligned with saidsecond stacking device when said second stacking device is in saidunloading position, such that a stack delivered from said secondstacking device is raised by said first conveyor to said upper positionand subsequently transported to the final stack delivery conveyor whensaid first stacking device is set to said unloading position.
 6. Amethod for high speed continual stacking of a plurality of sheetsreceived from an initial sheet delivery conveyor, the stacked sheetsbeing delivered to a final stack delivery conveyor, comprising the stepsof:(a) receiving at least a portion of said plurality of sheets from theinitial sheet delivery conveyor into a stacking device of apredetermined capacity; (b) forming a stack from said at least a portionof said plurality of sheets in said stacking device; (c) determiningwhether said stack has reached the predetermined capacity; (d) settingsaid stacking device to a stacking position when the predeterminedcapacity is not reached, performing said steps (a), (b), and (c) untilsaid predetermined capacity is reached, and setting said stacking deviceto an unloading position when the predetermined capacity is reached todeliver said stack formed at step (c) to the final stack deliveryconveyor; (e) directing said plurality of sheets away from said stackingdevice to another stacking device of a predetermined capacity when saidstacking device is set to said unloading position at said step (d), saidanother stacking device being substantially identical to said stackingdevice; (f) setting said another stacking device into a stackingposition when said plurality of sheets is directed to said anotherstacking device at said step (e); (g) performing said steps (a), (b),and (c) for said another stacking device until the predeterminedcapacity is reached, and setting said another stacking device to anunloading position when the predetermined capacity is reached to deliversaid stack formed at step (c) to the final stack delivery conveyor; (h)directing said plurality of sheets away from said another stackingdevice to said stacking device when said another stacking device is insaid unloading position; and (i) setting said stacking device into saidstacking position to receive said plurality of sheets, such that saidstacking device and said another stacking device alternate in formingstacks from said plurality of sheets received from said initial sheetdelivery conveyor and in unloading said stacks to the final stackdelivery conveyor, thereby continually producing stacks of sheets.